Biodegradable polymers have been suggested as an alternative to synthetic polymers, which are one of the major causes of serious environmental pollution. Among various biodegradable polymers currently being developed, poly-β-hydroxybutyrate, a biodegradable polymer stored by various microorganisms in a state of unbalanced nutrition, has excellent characteristics such as biodegradability, water-resistance, piezoelectricity and biocompatibility. In particular, 4-hydroxybutyrate, an example of polyhydroxyalkanoate (PHA), has polyester-like characteristics and exhibits a wide range of properties from those of crystalline plastic to highly elastic rubber. Therefore, a considerable amount of research into microbial biodegradable plastic is presently being conducted.
Further, 4-hydroxybutyrate can be easily converted into various chemicals having 4 carbon atoms, such as 1,4-butanediol, γ-butyrolactone (GBL) and THF. In particular, 1,4-butanediol is an important industrial chemical in various forms such as polymer, solvent and a fine chemical intermediate. Although most chemicals having 4 carbon atoms are currently synthesized from 1,4-butanediol, maleic anhydride and so on, increasing production costs caused by an increase in the price of oil is necessitating development of another process for compensating and substituting a conventional chemical production process. A biological process has been suggested as such an alternative.
Meanwhile, succinate, dicarboxylic acid having 4 carbon atoms, is a kind of organic acid produced when a microorganism is cultured in an anaerobic condition. Now, various microorganisms are used as succinate-producing cells, and its production cost has become lower due to an effective fermentation process and development of a separation and purification process. Also, 4-hydroxybutyrate may be produced from succinate, and various organic acids having 4 carbon atoms can be derived from 4-hydroxybutyrate.
PCT Publication No. WO 2005/052135 is an example of a patent application disclosing a method of efficiently producing succinate, in which a Lumen bacterial mutant produces succinate in high concentration without producing other organic acids, and a method of preparing succinate using the mutant. In addition, a method of preparing an E. coli mutant capable of producing succinate in high concentration is disclosed in Korean Patent Application No. 10-2004-60149, and a method of preparing succinate using a novel gene is disclosed in Korean Patent Application Nos. 10-2005-0076301, 10-2005-0076317 and 10-2005-0076348.
As explained above, there is strong demand for a mutant capable of producing 1,4-butanediol, an industrially important chemical having 4 carbon atoms, and a biological method of preparing 1,4-butanediol using the mutant.